This project will analyze behavioral and pharmacological determinants of two prevalent forms of licit human drug taking behavior: cigarette smoking and coffee/caffeine self-administration. A series of five cigarette smoking studies will be conducted with subjects participating on an outpatient basis. Within a laboratory setting volunteer subjects will be permitted to smoke cigarettes under semi-naturalistic conditions which permit accurate measurement of number of cigarettes smoked, the duration and distribution of individual cigarette puffs, the volume and duration of inhalation and exhalation, and carbon monoxide levels in expired air. Two experiments will extend previous research of the effects of commonly taken psychoactive drugs on smoking by characterizing the effects of diazepam and chlorpromazine on smoking in both normal and drug abuser subjects. Two other experiments will provide information about pharmacologically-specific mechanisms in the control of smoking by characterizing the effects of pre-session administration of nicotine (via nicotine-containing gum) and inhaled carbon monoxide on cigarette smoking. A final cigarette smoking experiment will involve a direct experimental analysis of variables controlling some of the most important topographical aspects of smoking: puff volume, inhalation volume, inhalation duration, and carbon monoxide exposure. Concurrent with the smoking studies, a series of six coffee/caffeine studies will be conducted with subjects with histories of heavy coffee drinking who will reside in an inpatient research ward. Two experiments will provide information about caffeine reinforcement by using choice procedures to assess preference between caffeinated and decaffeinated coffee and by characterizing self-administration in the absence of coffee. Three experiments will investigate tolerance and cross-tolerance to caffeine by studying the effects of chronic caffeine consumption on the subjective, behavioral, and physiological effects of a wide range of doses of caffeine, d-amphetamine, and diazepam. A final study will investigate possible subjective, behavioral, and physiological effects of coffee constituents other than caffeine by evaluating caffeinated and decaffeinated coffee when administered under blind (in capsules) and nonblind (in beverage) conditions. In addition to providing new information about determinants of two licit forms of drug taking behavior which produce significant health risk, these studies will provide an improved understanding of the nature of the addictive process.